K. Ravindranath

Bio: K. Ravindranath is an academic researcher. The author has contributed to research in topics: Polycarbonate & Bisphenol A. The author has an hindex of 1, co-authored 1 publications receiving 30 citations.

Solid-state polymerization of poly(aryl carbonates): a facile route to high-molecular-weight polycarbonates

Abstract: It is reported that, under carefully controlled conditions, poly(aryl carbonate) can undergo chain extension in the solid state to substantially high molecular weight polymers. The increase in molecular weight was also accompanied by an increase in the polymer cryustallinity

Green and Sustainable Chemistry in Practice: Development and Industrialization of a Novel Process for Polycarbonate Production from CO2 without Using Phosgene

Abstract: This review focuses on the world’s first process succeeded in development and industrialization by Asahi Kasei Corp. for producing an aromatic polycarbonate (PC) using CO2 as starting material.1 The carbonate group of PC links directly to the residual aromatic groups of the bisphenol. Until Asahi Kasei’s new process is revealed, all of carbonate groups of PC in the world were derived from CO as starting material. Furthermore, more than about 90% of PC has been produced by so-called “phosgene process”, and the PC contains Cl-impurities. It needs to use not only highly toxic and corrosive phosgene made from CO and Cl2 as a monomer, but also very large amounts of CH2Cl2 and water, and needs to clean a large amount of waste water. The new process enables high-yield production of the two products, Cl-free and high-quality PC and high-purity monoethylene glycol (MEG), starting from ethylene oxide (EO), by-produced CO2 and bisphenol-A. PC produced by the new process has many excellent properties compared with conventional PCs. The new process not only overcomes drawbacks in the conventional processes, but also achieves resource and energy conservation. The reduction of CO2 emissions (0.173 t/PC 1 t) is also achieved in the new process, because all CO2 is utilized as the component consisting main chains of the products. The newly constructed commercial plant of Chimei-Asahi Corp. (Taiwan), a joint venture between Asahi Kasei Corp. and Chi Mei Corp., has been successfully operating at full-production since June 2002. The initial capacity (PC:50,000 t/y) is now increased to 150,000 t/y. A typical example of the Green and Sustainable Chemistry (GSC) contributing to society and mankind has been realized.

Crystallization and Solid-State Polymerization of Poly(bisphenol A carbonate) Facilitated by Supercritical CO2

Abstract: Poly(bisphenol A carbonate) was synthesized by solid-state polymerization (SSP) using supercritical CO2 to induce crystallinity in low molecular weight polycarbonate beads. The CO2-induced crystallization was studied as a function of time, temperature, molecular weight, and pressure. There was an optimum temperature for crystallization which depended on the molecular weight of the polymer. The molecular weight and percent crystallinity of the polymer produced by SSP were determined as a function of time and radial position in the bead. The molecular weight and percent crystallinity were strong functions of the particle radius, probably because of the slow diffusion of phenol out of the polymer particles. Nitrogen and supercritical CO2 were used as sweep fluids for the SSP process. The polymerization rate was always higher in supercritical CO2 at otherwise comparable conditions. We hypothesize that supercritical CO2 plasticizes the amorphous regions of the polymer, thereby increasing chain mobility and the...

Synthesis of High Molecular Weight Polycarbonate by Solid-State Polymerization

Abstract: The solid-state polymerization (SSP) of small particles (20 μm) of poly(bisphenol A carbonate) resulted in high molecular weight material (Mw of 36 000 g/mol). Molecular weight distribution broaden...